Opera mail (external client) - how to change mail storage folder?

I know how to change mail storage folder in M2 (built-in browser Opera Mail Client) but i cannot do the smae trick with Opera Mail (external mail client), i would like to move the folder away from C:\drive. There is no line in /users/user/appdata/roaming/operamail/opera/operaprefs.ini

Just make sure to do it while Opera Mail is closed and move your mail folder to that spot before you start Opera Mail.

In other words, opera:config is an interface to the settings in operaprefs.ini. So, you can just use opera:config in Opera 12 to see what you have to add/set in Opera Mail's operaprefs.ini. Or, you can just add opera:config back to Opera Mail.